FR2764280A1 - PROCESS FOR THE MANUFACTURE OF CARBON 60 - Google Patents

Abstract

The invention relates to a method and a device for the continuous production of carbon black with a high fullerene content. The device essentially consists of a plasma reactor (1), a downstream heat separator (2) to separate the non-liquid constituents and a cold separator (3) attached thereto.

Description

t-1 2764280 Process for the production of Carbon 60 The pre ,, ent memory

  describes a method for continuously and economically manufacturing concentrated carbon 60. It is essentially characterized by an improvement in the methods described in B.F 9201554 and in PCT 9400321. supplemented by a separation and concentration device. It was described. especially in the US patent. 5227038, a laboratory device used to produce a few grams of fullerenes by the action of an electric arc between electrodes in

  carbon used as raw material and this discontinuously.

  Besides that the quantities produced are minute, the concentration of C60 in the carbonaceous soots deposited are themselves very low. never exceeding 10% of the mass produced. In addition, the C60 is found in this process. mixed with higher fullerene compounds, requiring

  costly fractionation poulr be isolated to sufficient purity.

  In US Patent No. 5,304,366 describes a process allowing a certain concentration of the product, but it implements a high temperature filtration system of the gas circuit, which is good

  difficult to achieve partically.

  In BF 9201554 as well as in patent EP 0682561 and and PCT 9400321, there is described a general process for the production of carbonated soot with nanostructure defined by the action of a gaseous plasma on carbon at high temperatures. In one of the product ranges thus obtained, during sufficient processing temperatures, fullerenes can be obtained continuously and industrially. However. without the improvements that we have now described. the reaction products obtained (ILI process, as described. are very impure and also contain, at best, 10% of carbon mlahn2èl to higher fullerenes as well as to carbon not transformed into fullerenes The applicant has found a way to overcome the disadvantages mentioned above by supplementing the

  following the above-referenced method.

  Figure I is used to support our description. It comprises at I the reactor modified as indicated.

  The reactor is arranged so as to comprise two distinct but contiguous zones. Zone A, reserved for the reaction in the part maintained at very high temperature, is insulated as much as possible thanks to a lining 2 to ensure maximum use of the energy developed by the

pl a '-, l] s a.

  The temperature v is notably maintained above 4000 C to obtain a minimum volatization of the reactional carbon. Zone B, on the contrary, is cooled with sufficient efficiency to maintain the aerosol produced in A at a temperature between 1000 and 2000 C for a defined period. It is indeed, in this phase that the gaseous carbon molecules from A are

  recombine with each other to give rise to fullerenes and mainly carbon 60.

  The reactor is supplied with helium as plasma gas and with graphite as a raw material. Its operating temperature is adjusted by all known means as indicated, so that the carbon 60 produced is in the gaseous state mixed with the plasma gas. In part B of the reactor, the temperature is preferably maintained within the desired range thanks to an injection at

  debhil tdél'ini dc ga 'plitsnia2bne f1oid.

  In it leads inlfrlieLIur of reactor I. the circulating niélange thus consists of a plasma gas, die carbon 60 in the gaseous state and various forms of non-gaseous carbon, that is to say of a part

  die first unprocessed nilth and heavy non-vaporizable fullerenes.

  The separation device 3 consists of a cyclone-effect cylinder well known to those skilled in the art.

  Convenablenlient diniensataire comnpte minus gas flow rates used. it allows a separation at more than 90 I of efficiency (the solid parile contained in the aerosol leaving the reactor I It thus makes it possible to eliminate from this gas flow the most important part of the carbon and which is not under the form of C60, itself volatile and remaining mixed in gaseous form with plasimagen gas The apparatus 3 is kept isothermal by all known means so as to avoid any condensation of carbon 60 in any of its parts. 5, at the base of the separator 3 makes it possible to continuously extract and recycle the carbon not transformed into C60 in the gaseous circuit maintained in a closed circuit tr [ice in the ventilator- 6. The applicant has found this way of proceeding particularly advantageous because el] e \ é high consumption of raw material and facilitates the transformation into carbon 60

  car-blones having already crossed the plasma zones and are found in a very divided form.

  The separation apparatus 3 is followed by an apparatus of the same type 4. but cooled. by all known means * at a temperature lower than that of the condensation of carbon 60. Advantageously, the apparatus will be cooled below 100C by a double jacket of water, supplied by the conduit 9

and evacuated via line 10.

  In this second separator, a powder is collected consisting of a mixture of carbon 60 and a little other carbon entrained by the gases from the separator 3, the proportion of this being a function of the efficiency of the separator 3. We here we underline the fundamental principle of the claimed process. In fact, if the proportion of C60 relative to the total hardly exceeds a few percent in the aerosol from reactor I as experience shows. the separation prior to condensation of the desired product from other carbons leads, with a usual separator yield of 90 c, to a mixture at the base of the separator 3 containing up to 40% of C60. Thanks to the lock 7. the raw product 8. resulting from the process therefore contains significant quantities of C60, facilitating

  much further processing.

  The plasmiagen gas from the separator 4 is recycled by the fan 6 in the reactor 1 through the pipe 1 1. LUne bypass of this gas by means of the member 13 makes it possible to recycle part of the cold current making it possible to maintain part B of the reactor I at the desired temperature. Material carbon supply

  first is carried out by the device 12, the addition of plasrnagenic gas by the nozzle 14.

  We now describe more precisely the upper part of the reactor I in FIG. 1. FIG. 2

  represents the arrangement according to the invention. Figure 3 a sectional view of this part.

  a metallic cylindrical enclosure I with a double envelope 2 ensures the rigidity of the reactor and its thermal security. The double jacket serves as cooling means in order to dominate, taking into account the exceptional conditions prevailing in the enclosure. the thermal effects given off. A refractory lining 3. made of graphite. defines the geometry of the effective part of the reactor. Its thickness is chosen so as to produce a well-defined reaction laboratory. She may be

  between I and 10 cm for example.

  The electrodes 4, 5 and 6 are arranged as shown in FIG. 3, at 120: one with respect to the other and with an inclination allowing a convenient ignition of the plasma initiating arc. The electrodes are movable in the vertical direction and can be connected to a device of the type used in three-phase arc furnaces. This ensures the consistency of the electrical characteristics at the level of the electrodes. The three-phase power supply is also similar to those used in

  the electroclimatic industry for three-phase arc furnaces.

  1 es. 1c ade- (Cs 4.5 C 6 oulissent. Towards the reactor coLuvercle through the press-

e1hupócs adequtlats.

  The electrodes are made up of cylindrical harrows of a few dimensions of (diameter, of a

  lengthCI ilndlinie. and in as pure graphite mail as possible.

  L1e conduil 7 ecrl to the introduction of the mixture of plasma gas and carbonaceous raw material, plus one less mixed with the recycled products from reactor 3 of Figure I1 The plasnmagen gas enters the reallower by the only conduit 7 unlike which has been described in BF 93011554 where it surrounds each electrode by furnaces specially fitted out for this purpose. There is a significant improvement in the technology described above and which is made

  possible in the particular case of manufacturing the C60 by this device.

  PIlasnLagène gas consists of a rare gas containing helium. either pure helium, or a mixture of helium with another rare gas. Any gas reacting at any tempe rature whatsoever with carbon is prohibited. A supply of fried plasma gas can be made in the circuit to compensate for any technological losses. Top up via the conduit 14. figure I is provided In this

oe1k t.

  The reaction temperature is maintained above 4000C. so as to ensure volatilization

  as much carbon as possible.

  Lat Figure 3 shows a sectional view of the reactor described above. We have numbered the same elements with the same figures. We will recognize in particular the force I and 2 enclosures. The graphite packing 3. the three electrodes 4, 5 and 6 arranged at 120 relative to each other as well as the conduit 7 allowing the suspension of carbon

in plasnmagen gas.

  The raw material used as a carbon source consists of finely ground graphite, acetylene type black, degassed carbon black, ground pyrolytic carbon or a mixture of these materials. The carbon content of the starting material should be as high as possible and preferably greater than 99%. It is clear that any material having a lower carbon content will contain impurities which are troublesome from two points of view. Firstly. some of them like hydrogen. oxygen or sulfur reduce the yield of C60 production, other compounds being synthesized in parallel. On the other hand, any impurity found in gaseous form in the manufacturing cycle circuit will cause a reduction in the purity of the plasma gas and will not require contributions of the same pure gas to maintain the original composition, the plasma gas

should be as pure as possible.

  We now give, by way of non-limiting example, a few exemplary embodiments according to the invention.

Example 1

  The device according to FIG. I consists of a cylindrical reactor with an internal diameter of 300 min. a height of 150 cm and a double jacket of water circulation cooling. Between the graphite lining and the inner wall of the fori-ce enclosure, there is an insulating layer in

  carbon foam to ensure maximum thermal concentration at the plasma level.

  Three graphite electrodes with a diameter of 20 mm are positioned by a device sliding through the reactor cover by cable glands contained in electrically insulated sleeves. A central duct with a diameter of 20 mm allows the introduction of the graphite suspension into the plasma gas. The electrodes are supplied by an electrical source of a hundred k \\ W, capable of delivering voltages between 50 and 500 Volts and intensities between 200 and 2000 A. UL'n three-phase regulator of the type used in the arc furnace ensures relative consistency of the electrical characteristics at the plasma level. The state of the art in this field allows this kind of regulation to be obtained with variations less than 10 due with respect to the characteristics.

desired.

  Lc ga / iplaunalgène is pure heliuml in cilrculation1, the necessary supplementation corresponding only to the technological skins. all of the initallation being autolmatically maintained at a light level

  stpre ,,, ion compared to I'anlbianle. suffianllte to avoid said technological pearls.

  The upper part of the reactor is maintained thanks to the incoming flows and the electric power

  delivered at a temperature between 4000 ° C. and 5000 ° C.

  The lower straw of the reactors is supplied with cold recycling gas so as to maintain its

  temperature at a value between 1200WC and 1600 C.

  The raw material is micron graphite.

  - \ with a flow rate of 10 m3 / h of, az at the level of the introduction into the reactor and an additional material of 2 kg / h. it is established. after one hour of operation a steady state generating in the reactor 3. maintained at high temperature, a flow of recycled carbon through the valve 5, of the order of 8 kg / h. which means that at the level of the introduction via the conduit I 1, the carbon flow rate is established at around 10 kg / h. With a power of 100 kW, the applicant has found that approximately 6% of the carbon thus introduced is transformed into C60 gas, mixed with carbon not converted to C60 and helium. The efficiency of the cyclonic separator 3 is such that 90% 7 of the unprocessed carbon

  is folded down and recycled while the cooled separator 4 receives the rest of the gas flow.

  This gas consists of an aerosol of unprocessed carbon, solid C60 and Helium. The product which collects at the base of the cyclonic separator 4 and discharged at 8 consists of a product containing 30 <I of C60 mixed with unprocessed carbon. This carbon contains part of the starting graphite and some higher fullerenes such as C70, C84 and fragments of fullerenes

of all kinds.

  The crude product, discharged at 8 representing approximately 2 kg / h at 30% C60 can be used as it is or purified by any known means so as to extract the pure carbon 60 therefrom. The production in this

  example comes out at around 0.6 kg / h of pure carbon 60.

Example 2

  The operation is carried out as in Example 1, but the cyclonic separator 4 is replaced by a condenser at a temperature close to the asbestos and supplied directly with a solvent cooled in a closed circuit. This

  A liquid curtain device is common in extractive techniques.

  The entire production is thus reduced in the form of a suspension of carbon in the tandi solvent, which the helium is recycled (in the same way with, as a precaution, to retain on the circuit

  by an ah, adequate orbiting traces of solvent which may remain in suspension.

Example 3

  The procedure is as in Examples 1 and 2, but as a plasma gas is used a rare gas different from helium such as argon for example. Under these conditions, an adaptation of the voltages and intensities must be carried out due to the different behavior of the plasma gas. It is also possible to use a mixture of rare gases such as for example a mixture of argon and helium in all

prOlport ions ,.

Example 4

  The procedure is as in Example 1, but a filter cartridge made of a material resistant to the temperature of the aerosol is inserted between the chambers 1 and 4 of FIG. 1. This filter can be constituted (porous ceramic or porous carbon for example. The gas flow leaving the filter and entering

  in the separator 4 then only consists of helium charged with gaseous fullerenes.

  This cartridge then replaces the hot separator 3. Under these conditions the separator 4 condenses the concentrated C (-) O. The recycling of carbon from the filter cartridge then represents a mass of about 90 of the total carbon introduced into, the production reactor I. It is of course possible, ax cc this mode of floatation. (replace helium with another rare gas or a mixture of gases

It is a helium binder.

y5- 2764280

Example 5

  The procedure is as in Example I. but using as carbonaceous raw material black of

  black typ of acetvlene made up of micrographitic, even nano-graphitic particles.

  The results are very few identical things. after a period of continuous operation of the apparatus. LI only difference in operation comes from the presence of traces of impurities

  cntlenIUes dan's this type of black. traces which are found in the gas circuit and in the raw product.

Example 6

  The procedure is as in Example 5, but carbon black with a purity greater than 99% carbon and free of heavy elements is used as the carbonaceous raw material. The black used must first be degassed by any known means so as to avoid contamination of the gas circuit

  plamag; ene. It is thus possible to use carbon black or finely ground pyrolytic carbon.

Claims (1)

Claims * Pi (c.dl ctlintlu for the carbon lbricaltion 60 caICLriN ,, cnce that we realize cse ,,, nicllcmcnIl L in cjlatrc cClceiltes SLuCCesivCes los l pedrations LUI \ aIllCS, '- dan, a reaction vessel filled of a refractory coating and protected by a cooling jacket, partial vaporization of carbon is carried out in suspension in an inert plasma gas, an average temperature above 4000 C obtained by the action of a three-phase plasma. contiguous to the first, all the known means are cooled to a temperature of between 1000 ° C. and 2000 ° C. the flow from the previous enclosure. - in a hot separator in which the aerosol produced in the preceding enclosures is admitted temperature at a value higher than that of the sublimation of carbon 60 but lower than that of the vaporization of higher fullerenes, the forms of carbon not transformed into C60 being recycled at the head of the reaction vessel. - In a cold separator, the temperature is maintained at a low enough value to condense the carbon 60 vapor contained in the gas mixture leaving the hot separator, the carrier gas being recycled as plasma gas in the first enclosure. 2 * Method according to 1. the reaction vessels being lined with an interior coating of graphite. 3 * Method according to one of the preceding claims, the plasma-bearing gas consisting of helium. s Method according to 3. the plasma-bearing carrier gas consisting of a rare inert gas with respect to carbons in any proportion with helium. t Method according to one of the preceding claims, the carbonaceous raw material being graphite. 6 Method according to 5. the raw material being a carbon black containing more than 99% of carbon. 7 À Process according to 6. the raw material being acetylene black. d Process according to 6. the raw material being carbon black degassed and stripped of its non-carbon impurities. 9 * Process according to 6. the raw material being finely ground pyrolytic carbon.   1 O Carbon 60 obtained by any one of the preceding claims.